1. Field of the Invention
The present invention relates to a method, system, and an article of manufacture for performing registration calibration for printing devices.
2. Description of the Related Art
A color printer may achieve a desired color during printing by overlaying colors, such as cyan, magenta, yellow and optionally black, on top of each other in separate color planes. Achieving proper color registration in a printer involves calibrating the color printer such that the color planes are overlaid precisely on top of each other at every pixel. If a given printer""s color is misregistered, improper colors and artifacts may appear on the printed page.
To achieve color registration, a printer first prints one or more predetermined registration marks, such as a pattern of small intersecting lines, on a print medium. Subsequently, an operator examines the printed registration marks and adjusts the printer to compensate for the detected deviations between the printed registration marks and the corresponding predetermined registration marks.
Since color registration of a printer can change during printing, printers may need periodic color registration even while printing a print job. In a high-speed printer that prints a large number of pages continuously, an operator may have to stop a print job to manually adjust the printer. The manual operator adjustments may be augmented by automated color registration by using density measurements of registration marks as described in U.S. Pat. No. 6,198,549 entitled xe2x80x9cSystem, Method, Program and Print Pattern for Performing Registration Calibration for Printers by Measuring Density,xe2x80x9d which patent is incorporated herein by reference in its entirety. However, density measurements of the registration marks cannot fully correct for color misregistration.
Hence, there is need in the art to provide improved techniques for automated color registration in printers.
Provided are a method, system and article of manufacture for registration calibration of an operating printing device. A test pattern is printed on a print medium and an imaging device generates a digital image of the printed test pattern. An interference pattern corresponding to the digital image is analyzed and based on the interference pattern the printing device is calibrated. In one implementation the interference pattern is a Moire pattern. In another implementation, the calibration is performed while continuing to process a print job via the operating printing device, wherein the steps of printing, generating, analyzing, and calibrating are performed repeatedly.
In one implementation analyzing the interference pattern further comprises isolating via edge detection the interference pattern from the digital image. The interference pattern is compared to the test pattern. Based on the comparison, a determination is made as to whether a calibration of the printing device needs to be performed.
In another implementation, the printing device has a plurality of printing stations, wherein the test pattern is printed on the print medium by the plurality of printing stations, wherein the printing stations print with a printing medium, wherein the printing medium is from the group consisting of ink or toner, wherein the printing is with at least colors from the group consisting of cyan, magenta, black, highlight and other colors, and wherein the scanning device generates the digital image of the printed test pattern after the test pattern has been printed by at least two of the printing stations.
Implementations are provided wherein the printing device is from the group consisting of a color printer, a photocopier, a color fax machine, a laser printer, an electrostatic printer and an ink-jet printer, wherein the test pattern is a reticle pattern, wherein the print medium is selected from the group consisting of paper, transparency, fabric, plastics, labels, metal, cardboard, and container, wherein the container is selected from the group consisting of plastic, cardboard and metal, and wherein the imaging device is selected from the group consisting of a scanner and a CCD camera.
The implementations enable automated color registration of a printer during printing. A printer prints reticle patterns on a print medium. If the printer is misaligned, the printed reticle patterns exhibit Moire patterns. The Moire patterns offer rich clues on the nature of the misregistration of the printer, and enable an application to correct for printer misregistration. The implementations also allow for periodic automated color registrations while the printer prints a long job, without stopping the job.